Shoulder arthroplasty instrumentation

ABSTRACT

Patient specific shoulder component implant instruments are described for hemi and total, normal and reverse shoulder arthroplasty.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/152,845, filed Oct. 5, 2018, titled “SHOULDER ARTHROPLASTYINSTRUMENTATION,” now U.S. Patent Application Publication No.2019/0269415, which is a continuation of U.S. patent application Ser.No. 15/443,333, filed Feb. 27, 2017, titled “SHOULDER ARTHROPLASTYINSTRUMENTATION,” now U.S. Patent Application Publication No.2018-0014835, which is a continuation of U.S. application Ser. No.13/075,378, filed Mar. 30, 2011, titled “SHOULDER ARTHROPLASTYINSTRUMENTATION,” now U.S. Pat. No. 9,579,106, which claims the benefitof and incorporates herein by reference both U.S. Provisional PatentApplication No. 61/319,484, filed Mar. 31, 2010 entitled “PATIENTSPECIFIC INSTRUMENTS” and U.S. Provisional Patent Application No.61/325,435, filed Apr. 19, 2010 entitled “REVERSE TOTAL SHOULDERARTHROPLASTY INSTRUMENTATION.”

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare incorporated herein by reference in their entirety to the sameextent as if each individual publication or patent application wasspecifically and individually indicated to be incorporated by reference.

FIELD

The present invention relates to patient specific instrumentation tofacilitate implantation of a total shoulder joint and to the process andtechnique for creating the instruments.

BACKGROUND

Shoulder hemiarthroplasty is commonly used to treat patients withglenohumeral joint arthrosis. Total shoulder arthroplasty may beindicated for patients without a good articular surface on the glenoidat the time of surgery. For patients with glenohumeral joint arthrosisand an additional deficient rotator cuff, reverse total shoulderarthroplasty may be indicated. The 12%, 15%, and 22% revision rates,respectively, remains high compared to hip and knee arthroplasty.Glenoid component loosening and instability are important complicationsand may be caused by poor positioning of the component. An accurateplacement of the complementary humeral cut is also important to achievea stable joint.

There is a continuing need to improve the instruments used to facilitatethe implantation of total shoulder joint components.

SUMMARY OF THE DISCLOSURE

Patient specific instruments according to the invention carry surfacesand features that facilitate implantation of shoulder implantcomponents. These surfaces are patient specific and they conform to theactual diseased joint surfaces presented by the patient. In use thephysician uses the instruments to align and direct surgical cuts, toprepare the patient to receive an otherwise standard and conventionaljoint components of either “normal” or “reverse” configurations.

The process of the invention that results in the creation of a set ofpatient specific instruments takes a computed tomographic (CT) ormagnetic resonance imaging (MRI) file of the patient's shoulder andpresents it to a user on a computer screen. The user using a mouse orother pointing device defines reference points on the image to definegeometric axes, planes and offsets. Next the user imports and aligns acomputer automated design (CAD) file of the implant component with thenative anatomy. The image of the implant component is merged anddisplayed with the anatomy image. Using a rule based system the userfinds an optimum location for the glenoid component of the implant. Oncethe optimum location for the glenoid component is defined a custominstrument CAD file is created and a glenoid placement instrument ortool is generated from the file using conventional techniques. The toolis formed from plastic and/or metal that can be sterilized and useddirectly in the surgery.

In general the glenoid instrument consists of an oval or egg shaped“disk” with a protruding stalk like “handle”. The disk has an uppersurface and a lower surface, and a side wall separating the two.

In general the humeral instrument consists of a “cap” like structureconnected to an offset “block” feature. There is a clearance volumebetween the “cap” and “block”. The cap has an inner surface and an outersurface.

With the glenoid instrument defined and created a companion humeralcutting instrument is generated to guide the resection of bone inpreparation for the implantation of the humeral component of the totalshoulder implant system. The humeral instrument is likewise defined andmanufactured from sterilizable plastic and/or metal in a process similarto the glenoid component. The instruments are used together and theyshare several characteristics.

The glenoid instrument has a complementary surface to a surface of thediseased joint formed in the lower surface.

The glenoid instrument has one or more index surfaces adjacent to itsarticular lower surface that facilitate placement of the tool duringsurgery.

The glenoid instrument has windows to permit visual confirmation ofplacement.

The glenoid instrument has a handle to assist in proper positioning ofthe instrument.

The glenoid instrument has holes that aid in defining the direction ofscrews should screw placement be pre-operatively determined.

The humeral resection guide instrument or humeral instrument has acomplementary surface matching the humeral head contour on its innersurface.

The humeral resection guide instrument has one or more index surfacesadjacent to its articular inner surface of the cap portion thatfacilitates the placement of the tool during surgery.

The humeral resection guide instrument has a block offset from the capthat includes a saw slot that directs the use of a surgical saw toremove the humeral head.

The humeral resection guide instrument has holes that accept pins orother fasteners which connect the block portion of the humeralinstrument to the proximal humerus bone.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures of the drawings like reference numerals indicateidentical structure, wherein:

FIG. 1 is a view of the glenoid component instrument;

FIG. 2 is a view of the glenoid component instrument;

FIG. 3 is a view of the glenoid component instrument;

FIG. 4 is a view of the glenoid component instrument;

FIG. 5 is a view of the glenoid component instrument;

FIG. 6 shows the humeral component cutting block instrument;

FIG. 7 shows the humeral component cutting block instrument;

FIG. 8 shows the humeral component cutting block instrument;

FIG. 9 shows the humeral component cutting block instrument;

FIG. 10 shows the humeral component cutting block instrument;

FIG. 11 shows the glenoid instrument in use placed against the glenoid;

FIG. 12 shows the glenoid instrument in use placed against the glenoid;

FIG. 13 shows the glenoid instrument in use placed against the glenoid;

FIG. 14 shows the glenoid instrument in use placed against the glenoid;

FIG. 15 shows the glenoid instrument in use placed against the glenoid;

FIG. 16 shows the humeral cutting guide block in use against the humeralhead;

FIG. 17 shows the humeral cutting guide block in use against the humeralhead;

FIG. 18 shows the humeral cutting guide block in use against the humeralhead;

FIG. 19 shows the humeral cutting guide block in use against the humeralhead;

FIG. 20 shows the humeral cutting guide block in use against the humeralhead;

FIG. 21 shows glenoid components in place;

FIG. 22 shows glenoid components in place;

FIG. 23 shows glenoid components in place;

FIG. 24 shows humeral components in place;

FIG. 25 shows humeral components in place;

FIG. 26 shows humeral components in place;

FIG. 27 shows a human shoulder joint;

FIG. 28 is a flowchart of the process for making the instruments;

FIG. 29 shows anatomic geometry;

FIG. 30 shows part of a step in the process;

FIG. 31 shows part of a step in the process;

FIG. 32 shows anatomic geometry;

FIG. 33 shows part of a step in the process; and

FIG. 34 shows part of a step in the process.

DETAILED DESCRIPTION Glenoid Component Instrument

FIG. 1 through FIG. 5 should be considered together as they show thesame glenoid component instrument 10 from several differentperspectives. The glenoid component instrument 10 has a handle 12attached to a generally oval or egg shaped disk shaped instrument body14. The disk shaped body 14 has a patient specific conformal lowersurface 16 that matches the surface of the articular portion of theglenoid joint. Adjacent the patient specific bottom surface 16 is a hooklike feature that matches an off articular bony portion of the glenoid.This hook 18 is also patient specific and one or more such hooks may beformed depending on the patient anatomy. These features are placed onthe sidewall 17 of the disk shaped instrument body. Also present areholes passing through the disk element of the instrument body from thelower surface to the upper surface. Holes useful for directing screws orthe like are seen at reference numeral 20 and 22. A hole or slot forcutting a keel slot or peg hole is seen at reference numeral 24.Additional holes acting as windows to allow visualization of the nativesurface are shown at reference numeral 23. Holes for bone pins can alsobe used to hold the glenoid instrument in place.

Humeral Component Cutting Block Instrument

FIG. 6 through FIG. 10 should be considered together as they show thesame humeral component instrument from several different perspectives.The humeral component instrument 30 has a generally cap shaped element31 with a patient specific conformal inner surface 32 that can wraparound the humeral head. There is also at least one guide surface 34feature that is patient specific and off the articulating surface of thejoint. Apertures labeled 36 and 38 in the form of windows are cutthrough the cap from the inner surface to the outer surface to permitvisualization of the joint surface. Adjacent to cap 31 is a blockfeature 39 having a saw guiding slot 40 that overlies several pin holestypified by hole 42. These holes may be used to place Steinman pins orother fixation devices. There will usually be three holes at differinginclinations to rigidly attach the cutting block 30 to the bone. Theblock element 39 is offset from the cap 31 element by a clearance space.The fixation devices traverse this clearance space when they are pushedinto position.

Use of the Glenoid Instrument

FIG. 11 through FIG. 15 should be considered together as they show thesame glenoid instrument in contact with the glenoid portion of theglenohumeral joint. Typically the physician holds the handle with hishand 50 and presses the instrument body against the joint surface 51.Tactile and visual clues that result from the patient conformal surfacesallow and facilitate registration of the instrument body with the nativeanatomy.

Use of the Humeral Head Cutting Block Guide

FIG. 16 through FIG. 20 should be considered together as they show thesame cutting block in contact with the humeral head. In use the capfeature overlays the humeral head 52 and the conformal inner surface andindex surface 34 align the instrument with the bone. Once the instrumentis fastened to the bone via fixation holes 42, the saw may enter slot 40and resect the bone. As seen best in FIG. 20 the clearance space allowsthe humeral instrument to accommodate muscle 37 and other tissue withminimal injury.

Glenoid Component in Position

FIG. 21 through FIG. 23 should be considered together as they show theglenoid implant component 62 in place on the glenoid. Both a “normal”glenoid component 62 is shown as well as a “reverse” glenoid component64 in dotted outline.

Humeral Component in Position

FIG. 24 through FIG. 26 should be considered together as the show the“normal” humeral implant component 66 in place on the humerus. FIG. 26and FIG. 25 depict a “reverse” humeral component 68 in place on thebone.

Overview of Instrument Creation and Use

FIG. 27 shows a human shoulder joint.

FIG. 28 shows a flowchart of the process beginning with the collectionof patient data in process step 100. This data is used by process 120 toconvert and display the native anatomy to a user. In process step 130the image data is used with implant specific data to design the twoinstruments. In process step 140 instrumentation data is used tomanufacture physical instruments. In process step 150 the surgeon usethe physical instruments to carry out the surgery.

Glenoid Component Instrument Creation Process

A software program Mimics® is used to take MRI or CT data and to createa 3-dimensional image of the glenoid and scapular spine that can bemanipulated on the computer screen. The user defines three points,including a glenoid center point in the center of the glenoid articularsurface, a junction point along the ridge of the scapular spine wherethe medial border and scapular spine meet, and an inferior point at themost distal end of the scapular spine. These three reference pointsdepicted in FIG. 30 are used to define a coronal plane, which may bedisplayed on the image. A transverse plane orthogonal to the coronalplane is created through the glenoid center point and scapular spinejunction point. Next a sagittal plane is created orthogonal to said twoplanes and centered on the center point of the glenoid as seen in FIG.30. A reference anatomic axis may then be defined as the intersection ofthe transverse and sagittal planes. These steps may also be performed ina conventional software package such as “Pro/E” from PTC softwarecompany in Needham Mass. which is widely used to define parts in the CADindustry.

In order to reproduce the normal anatomic orientation of the glenoidafter TSA, the ideal orientation of the glenoid component should have 4degrees of superior inclination and 1 degree of retroversion. Therefore,the central peg or keel should achieve this orientation given adequatebone stock. In reverse total shoulder arthroplasty, the glenoidcomponent should have 5 degrees of inferior inclination seen atreference numeral 200 in FIG. 29, close to neutral version, and slightinferior translation to minimize notching. This is seen in FIG. 29 andFIG. 32. Therefore, the inclination and version of the glenoid componentwill be referenced from the sagittal plane as defined. For example, theinclination plane can pass through an axis created by the intersectionof the sagittal and transverse planes at 4 degrees of superiorinclination as seen at reference numeral 210 in FIG. 29. A second axiscan then pass through the coronal and inclination plane. The versionplane can pass through said second axis at 1 degree of retroversion asseen at reference numeral 220 in FIG. 32. At this point, the versionplane will represent the proper orientation of the glenoid component;the glenoid component plane.

The alignment of the implant with the native bones is depicted in FIG.31. At this point the operator and likely physician will review theposition and size of the implant customized for this patient. With theimplant location and size determined, Pro/E is used to create a templateinstrument that will be used to help align the glenoid component duringthe surgery. A portion of the glenoid component instrument is designedto conform to the native bone. The first surface of said portion of theglenoid component instrument has a surface that is 3D inverse of thenative surface of the glenoid created via a Boolean subtractionoperation where the native surface of the glenoid is subtracted from thetemplate instrument. An approximately 1 mm gap between the bony surfaceof the glenoid and the inverse surface of the glenoid componentinstrument is added when using CT data to accommodate cartilage and/orslight errors in the reconstruction. This surface is created inGeomagic®. A second surface of said portion of the glenoid componentinstrument captures a bony surface close to but outside of the glenoidarticular surface. Said second surface is an extending feature that issimilarly created using a Boolean subtraction operation, and is used tohelp in the proper positioning of the instrument with respect to thebone. Said second surface wraps around the anterior aspect of theglenoid surface because it is easy to reference with a traditionaldelto-pectoral surgical approach, and can be used to lever theinstrument over the glenoid. At least one and perhaps as many as threesuch features around the perimeter of the glenoid will be defined forthe instrument depending largely upon the condition of the bonestructure, its geometry, and surgical exposure.

The glenoid component instrument has a set of apertures that canfunction as windows to observe tissue and or as guide to direct cuttingtools into the glenoid. For example, the instrument may carry a centerhole for a drill bit to pass for a central peg designed glenoidcomponent, or a slot to facilitate cutting a keel slot designed for aglenoid component. The orientation of the center aperture will be normalto glenoid component plane and be centered based on pre-operative plan.Peripheral holes in the instrument can be added to match any peripheralpegs/keels/screws or the like that the glenoid component may require.The peripheral holes will control the orientation of the glenoidcomponent in rotation about the central axis for the glenoid component.The location of the holes or windows or slots will determine therotation of the glenoid component. Next, the location of viewing slot(s)is defined for the instrument. These slots will be positioned so thatthey can be observed by the physician during the surgery and willcommunicate with the bony surface so that the presence or absence of abony surface in the window helps verify the seating of the instrument.The remainder of the glenoid component instrument includes an extendinghandle that is directed away (usually anteriorly) from the axis of thepeg/keel, as depicted in FIG. 15, in order to allow the drill to accessthe instrument.

For reverse total shoulder arthroplasty, a second glenoid componentinstrument can be used to target peripheral fixation screws for theglenoid component. After pre-operatively determining the depth of thereaming operation used to seat the glenoid component, the surgeon orengineer can pre-operatively determine the number, length, and alignmentof said peripheral fixation screws.

Said second glenoid component instrument will have a mating surface thatis the 3D inverse of the reamed surface. The second instrument has acenter hole in line with the central peg hole. In addition, peripheralholes in the second instrument will be in line with the pre-operativelyplanned screw locations. Drill taps will pass through said peripheralholes. The second instrument can also have as few as one mark on thevisible (lateral) surface (e.g. a mark pointing superiorly) to aid inthe rotational alignment of second instrument. During surgery, thesurgeon can use electrocautery to mark the surface of the glenoid (e.g.a mark pointing superiorly). The second instrument's mark can now bealigned to the glenoid's surface mark. Viewing slots on the instrumentwill allow the surgeon to verify the seating of the instrument on thereamed bone. A handle extends laterally from second instrument but willnot interfere with drill.

Bone modulus can be characterized from the Hounsfield unit obtained fromCT scans. Bone with higher modulus is stronger, and would be ideallocations for peg/screw fixation. The surgeon or engineer can use thisinformation to pre-operatively design the first and/or secondinstruments to direct the peg/screw into bone of higher modulus.

The process has created an instrument that can be used to define thelocation of a glenoid implant based upon an analysis of the native bonestructure in conjunction with a representation of the glenoid implant.

Humeral Head Cutting Block Creation Process

Similar to the glenoid component instrument, the humeral head cuttingblock utilizes MRI or CT data to determine the appropriate orientationand size of the orthopaedic component. For shoulder hemiarthroplasty andtotal shoulder arthroplasty, the position of the humeral component willbe 20 degrees in retroversion. For reverse total shoulder arthroplasty,it will be closer to neutral. In order to properly correct the versionof the humeral head, it is recommended that a MRI or CT scan of theelbow (same side) be taken as well. The diaphysis of the humerus will beapproximated to be a cylinder with its long axis to be defined as thelong axis of the humerus. Landmark points will be placed on the medialand lateral epicondyles of the distal humerus. A humeral coronal planepasses through said landmark points and is parallel to said long axis.The version of the humeral head will be offset from the coronal plane.If the elbow is not scanned, the calcar of the humerus can be used as areference when determining version angle as depicted in FIG. 33. Acalcar landmark point is identified. In this case, the version plane ofthe humeral component is defined as the plane that passes through saidcalcar point and the long axis of the humerus. Pre-operative sizing ofthe humeral head and humeral component can be performed. Humeral headresection and implant sizing performed pre-operatively on a lefthumerus.

The level of resection is built into the humeral head cutting block.Using MRI or CT data, this block engages with the humeral head by havinga backside face that is a 3D inverse of the native humeral head createdvia a Boolean subtraction operation where the native surface of thehumeral head is subtracted from a template block instrument. Anapproximately 1 mm gap between the bony surface of the humeral head andthe inverse surface of the humeral head cutting block is added whenusing CT data to accommodate cartilage and/or slight errors in thereconstruction. Said block engages the superior-medial aspect of thehead and has an additional feature that wraps around the lateral side ofthe lesser tubercle (subscapularis attachment sight) to additionally aidin the alignment of the block. The instrument has openings to allow thesubscapularis and rotator cuff to pass 5 without impingement as depictedin FIG. 20. The slot for the saw blade 40 is located approximatelyanterior to the humerus, and its cutting angle (approximately 45degrees) is dependent on the implant system being used. Said slot hasenough width to ensure that the blade remains parallel to the slot.

Other features include a minimum of two non-parallel pin holes for 10additional stability of the block to the proximal humerus. Said pinholes are located distal to the saw blade slot, and can accept pinsscrews or other fasteners. Viewing slots/portals on the block are usedto visually ensure that the instrument is fully seated onto the humeralhead. A targeting sight in line with the long axis of the humerus on thesuperior surface of the humeral head cutting block is used to target 15the humeral stem reamer.

The instruments will be steam sterilizable and biocompatible (e.g.DuraForm polyamide). Both the glenoid component instrument and thehumeral head cutting block have been prototyped and manufactured. Forthe proper execution of these instruments during surgery, it isnecessary to minimize the profile and volume of 20 these instruments asmuch as possible, as the surgical exposure for these types of proceduresare small. Modifications to these instruments continue to be made tomake the operative procedure more efficient and accurate.

What is claimed is:
 1. A set of patient specific surgical instrumentsfor positioning a glenoid component and a humeral component of ashoulder implant, the set of patient specific surgical instrumentscomprising: a glenoid instrument body fabricated specifically to have apatient derived surface computed from image data of a diseased nativeglenoid articular joint surface of the patient thereby creating anegative surface such that the glenoid instrument body has a surfacethat approximately matches and conforms to the diseased native glenoidarticular joint surface, the glenoid instrument body having one or moreapertures passing from an upper surface to the patient derived surface,at least one of the one or more apertures provided in a pre-surgicalplanned position within the glenoid instrument body to form an apertureto accept and orient tools used to prepare the diseased native glenoidarticular surface for the implantation of a prosthetic joint component;an index feature projecting from the glenoid instrument body fabricatedspecifically to have a patient derived surface for engaging a portion ofa shoulder anatomy of the patient to position and locate the glenoidinstrument body patient derived surface on the diseased native glenoidjoint anatomy; a humeral instrument body fabricated specifically to havea patient derived surface computed from image data of a diseased nativehumeral head surface of the patient thereby creating a negative surfacesuch that the humeral instrument body has a patient specific conformalinner surface that approximately matches and conforms to the diseasednative humeral head articular joint surface; the humeral instrument bodyhaving one or more apertures passing from an upper surface to thepatient derived surface; at least one guide surface feature extendingfrom the humeral instrument body that is patient specific and off thearticulating surface of the joint anatomy; and a saw guiding slot in ablock feature of the humeral instrument body.
 2. The patient specificsurgical instrument of claim 1, wherein the shoulder arthroplasty is atotal or a reverse shoulder arthroplasty.
 3. The patient specificsurgical instrument of claim 1, wherein the one or more aperturesincludes at least one cutting guide through the instrument body tolocate and direct cutting tools for aligning a portion of the glenoidcomponent for use in shoulder arthroplasty.
 4. The patient specificsurgical instrument of claim 3, wherein the portion of the glenoidcomponent corresponds to a keel or a peg component.
 5. The patientspecific surgical instrument of claim 3, wherein the patient derivedsurface of the instrument body and the index feature projecting from theinstrument body correspond to a pre-operatively planned location suchthat when the patient specific surgical guide is engaged with thediseased native glenoid articular joint surface the at least one cuttingguide has an orientation and location corresponding to the pre-operativesurgical plan.
 6. The patient specific surgical instrument of claim 5,wherein the pre-operatively planned location corresponds to a glenoidcomponent orientation of 1 degree of retroversion and 4 degrees ofsuperior inclination.
 7. The patient specific surgical instrument ofclaim 5, wherein the pre-operatively planned orientation is less than orequal to 0° of version.
 8. The patient specific surgical instrument ofclaim 1, wherein the index feature has a surface corresponding to anegative of the portion of the shoulder anatomy of the patient.
 9. Thepatient specific surgical instrument of claim 8, wherein the portion ofthe shoulder anatomy is the anterior aspect of said glenoid jointsurface of the patient.
 10. The patient specific surgical instrument ofclaim 1, wherein the patient derived surface of the instrument body andthe index feature projecting from the instrument body correspond to apre-operatively planned location and glenoid component orientation. 11.The patient specific instrument of claim 1, wherein the orientation andlocation of the index feature locates the aperture in a pre-operativelyplanned location, corresponding to component orientation of 1 degree ofretroversion and 4 degrees of superior inclination.
 12. The patientspecific instrument of claim 1, wherein the orientation and location ofthe index feature when engaged with the native diseased glenoid locatesthe aperture in a pre-operatively planned location with respect toretroversion and inclination corresponding to a component orientationfor a patient specific total shoulder arthroplasty procedure.
 13. Thepatient specific instrument of claim 1, wherein at least one of the oneor more apertures has a rectangular shape and the tool is a cuttingtool.
 14. The patient specific instrument of claim 1, wherein at leastone of the one or more apertures has a circular shape and the tool is awire.
 15. The patient specific instrument of claim 1, wherein at leastone of the one or more apertures has a circular shape and the tool is adrill bit.
 16. The patient specific instrument of claim 1, wherein atleast one of the one or more apertures has a slot shape to facilitatecutting a keel slot designed for the glenoid component.
 17. The patientspecific instrument of claim 1, wherein at least one of the one or moreapertures has a circular shape and the tool is a pin.
 18. The patientspecific instrument of claim 1, wherein the orientation and location ofthe index feature when engaged with the native diseased glenoid locatesthe aperture in a pre-operatively planned location with respect toretroversion and inclination corresponding to a component orientationfor a patent specific reverse shoulder arthroplasty procedure.
 19. Thepatient specific instrument of claim 1 further comprising: a handleprojecting from the instrument body.